Elastic moduli and hardness of η-Ta2N3 from nanoindentation measurements. (July 2015)

• Record Type: Journal Article
• Authors: Bourguille, Judith; Brinza, Ovidiu; Tétard, Florent; Nikitin, Sergey; Zerr, Andreas
• Is Part Of: Europhysics letters. Volume 111:Number 1(2015:Jul.)
• Page Start: 2282
• Page End: 63
• Publication Date: 2015-07
• Subjects: Physics -- Periodicals; Electronic journals; 530.05
• DOI: 10.1209/0295-5075/111/18006
• Languages: English
• ISSNs: 0295-5075

Abstract

<abstract> <title>Abstract</title> <p>Nanoindentation testing was used to determine elastic moduli and hardness of <italic>η</italic>-Ta<sub>2</sub>N<sub>3</sub>, a novel stiff and hard high-pressure compound recoverable at ambient conditions. For a sample having porosity of 14% we confirmed densification of its upper layer induced by mechanical polishing: At depths <inline-formula id="epl17214ieqn2"><tex-math><?CDATA ${<}400\ \text{nm}$ ?></tex-math><inline-graphic xlink:href="ark:/27927/pgj2j74g7s4" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /></inline-formula> we obtained <inline-formula id="epl17214ieqn3"><tex-math><?CDATA ${{\sim}10{\%}}$ ?></tex-math><inline-graphic xlink:href="ark:/27927/pgj2j74g7pg" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /></inline-formula> higher reduced elastic modulus <inline-formula id="epl17214ieqn4"><tex-math><?CDATA $E_{\mathrm{r}}$ ?></tex-math><inline-graphic xlink:href="ark:/27927/pgj2j74g7mc" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /></inline-formula> and <inline-formula id="epl17214ieqn5"><tex-math><?CDATA ${{\sim}25{\%}}$ ?></tex-math><inline-graphic xlink:href="ark:/27927/pgj2j74g7kt" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /></inline-formula> higher hardness when compared with the sample without the densified layer. Using the experimental values of <inline-formula id="epl17214ieqn6"><tex-math><?CDATA $E_{\mathrm{r}}= 238\ \text{GPa}$ ?></tex-math><inline-graphic xlink:href="ark:/27927/pgj2j74g7j8" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /></inline-formula> and of porosity we derived the shear modulus of dense <italic>η</italic>-Ta<sub>2</sub>N<sub>3</sub> to be <inline-formula id="epl17214ieqn7"><tex-math><?CDATA $G_{0}=124\text{-}144\ \text{GPa}$ ?></tex-math><inline-graphic xlink:href="ark:/27927/pgj2j74g7hq" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /></inline-formula>. Hardness of the porous <italic>η</italic>-Ta<sub>2</sub>N<sub>3</sub> was measured to be 18 GPa and its fracture toughness estimated to exceed <inline-formula id="epl17214ieqn8"><tex-math><?CDATA $3.2\ \text{MPa}\cdot \text{m}^{1/2}$ ?></tex-math><inline-graphic xlink:href="ark:/27927/pgj2j74g7g5" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /></inline-formula>. The Pugh criterion suggests a high malleability of <italic>η</italic>-Ta<sub>2</sub>N<sub>3</sub> which could explain the observed surface densification.</p> </abstract>